Biochemistry Unit-1: Henderson-Hasselbalch Equation

Hello friends, In today's article we see the Henderson-Hasselbalch Equation.

 Henderson-Hasselbalch Equation: 

Defination: 

                     ' The Quantitative relationship among pH, buffering action of a mixture of a weak acid with its the conjugate base, and the pKa of the weak acid is given by a simple expression called Henderson-Hasselbalch Equation.'

• The titration curves of acetic acid, H₂PO₄^- and NH₄⁺ have nearly identical shapes, suggesting that they all point towards a fundamental law.
• The Shape of the titration curve of any weak acid is expressed by the Henderson-Hasselbalch Equation.
• This equation is simply a useful way of restating the expression for the dissociation(pK) constant of an acid.
• For the dissociation of a weak acid HA into H⁺ and A^-, the Henderson-Hasselbalch Equation can be derived as follows ( see. image)
  
  
  

• This Equation fits the titration curve of all weak acids and enables one to deduce a number of important quantitative relations.
• Henderson-Hasselbalch Equation is of the great predictive valve in protonic equilibria as follow(see image)
  

• If the Equation is evaluated at several ratios of [ A^-]/[HA] between the limits 10³ & 10^-3, and the calculated pH value plotted(see image)
• The result obtained describes the titration curve for a weak acid as shown in the figure.  

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• This is all about the Henderson-Hasselbalch Equation.

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